Interleukin-33 (IL-33), also known as IL-1F11 or DVS27, is a member of the IL-1 superfamily of cytokines that is expressed mainly in stromal cells, such as epithelial and endothelial cells. The IL-1 family members and the IL-1 receptor family play an important role in inflammatory and immunological responses. IL-1 superfamily-related diseases include asthma, chronic obstructive pulmonary disorder (COPD), rheumatoid arthritis and psoriasis. IL-1 receptors have been used in the treatment of diseases. U.S. 2003/0049255 discloses a method of treating a patient affected with a medical disorder selected from the group consisting of rheumatoid arthritis, Alzheimer's, stroke, head trauma, myocardial infarction, heart failure, periodontal disease, inflammatory bowel disease, asthma and pancreatitis by administering a therapeutically effective amount of an IL-1 receptor and Interleukin-1 receptor accessory protein (IL-1RAcP), wherein IL-1RAcP may be soluble IL1-RAcP.
IL-33 plays a role in inflammation and several diseases, including asthma, rheumatologic diseases, inflammatory skin disorders, inflammatory bowel disease, central nervous inflammation, cancer, cardiovascular diseases (for a review, see Miller, 2011).
IL-33 seems to be a cytokine with a dual function, acting both as traditional cytokine and as intracellular nuclear factor with transcriptional regulatory properties (Haraldsen et al., 2009). IL-33 acts as a cytokine by binding to the ST2L/IL-1RAcP receptor complex (Chackerian et al. 2007). Signaling is then induced through the cytoplasmic Toll-interleukin receptor domain of IL-1RAcP.
IL-33 differs from other IL-1 family members by primarily inducing T helper 2 (Th2) immune responses in a number of immune cell types (Lamkanfi and Dixit, 2009).
In view of its important role in diseases, several strategies have been proposed to control pathogenic IL-33 expression. WO 2005/079844 discloses IL-33 antagonists, consisting of IL-33 or IL-33 receptor antibodies. Leung et al. (2004) describes a therapy of murine collagen-induced arthritis with soluble ST2, but they did not study the effect of the soluble receptor on IL-33. Hayakawa et al. (2007) shows that soluble ST2 blocks IL-33 signaling in allergic airway inflammation. However, although some improvement is obtained with these approaches, the blocking of the IL-33 response is rather weak and there is a need for better and stronger antagonists.
Surprisingly, it was found that a fusion protein comprising the soluble IL-33 receptor and the soluble IL-1RAcP efficiently inhibits the IL-33 response. The inhibition is not only stronger than the inhibition caused by soluble IL-33 receptor or by soluble IL-1RAcP alone, it is surprisingly also more efficient than a mixture of both soluble receptors.